Collaborize Classroom is an excellent free tool for online threaded discussion.  Online threaded discussion, or forums, allow students to respond to the original post/question AND respond directly to another student's post.  For example, this would differ from the Stevens Point Journal's commenting feature, where readers can only respond to the original post and not directly to another reader's post, which creates a long list of comments.  Collaborize Classroom is free and can also be used as a way to deliver digital resources to students.  If you are already a Moodle user, I would recommend using their forum feature instead.  For Edmodo users, I have contacted the company and they said they are currently working on developing a forum tool, but they did not give a timeframe for completion.

Online Discussion Topics

Whether or not you use Collaborize Classroom, the site provides great resources for using online discussion in the classroom and formulating questions, to include: